1. Field of the Invention
The present invention relates to an innovative image-capture apparatus and an innovative variable magnification lens, and particularly to a variable magnification lens preferable for a video camera use or a digital still camera use, and an image-capture apparatus using the lens. More specifically, the present invention relates to a variable magnification lens in which with a zoom lens as a base part, a lens group for increasing a focal distance at a telephoto end of the zoom lens is configured in an insertable and detachable manner to enlarge a variable magnification ratio, and a negative lens group is detachably configured in a front surface of the zoom lens to enlarge a variable magnification ratio toward the wide angle side, so that various types of aberration other than distortion aberration are favorably corrected, and an image-capture apparatus in which the variable magnification lens is used, a video signal obtained from an image-capture element is processed, so that the distortion aberration by the variable magnification lens is corrected to obtain an favorable image.
2. Description of Related Art
In Japanese Patent Application Publication No. 4-61570 (Patent Document 1), a video signal processing apparatus is proposed, in which distortion aberration caused by a lens is corrected by processing a video signal from a solid image-capture element.
Japanese Patent Application Publication No. 2005-352348 (Patent Document 2) shows that a configuration is preferable for achieving high magnification, in which in a 5-group zoom method constituted by an arrangement of positive, negative, positive, negative, and positive refractive powers in order from the object side, first, third and fifth lens groups are fixed, a second lens group is moved in an optical axis direction to vary power, and a fourth lens group performs correction of focal shift and focusing by zooming. There is provided an image-capture apparatus in which by the first lens group having a characterized lens configuration, a front lens diameter can be reduced in spite of a wide angle of view at the wide angle end, and distortion aberration, which would otherwise be difficult to correct, is corrected by the video signal processing according to Patent Document 1.
In Japanese Patent Application Publication No. 4-350815, (Patent Document 3), a constitution is shown, in which in a 4-group zoom method constituted such that positive, negative, positive, and positive refractive powers are arranged in order from the object side, first and third lens groups are fixed, a second lens group is mainly moved in an optical axis direction to vary magnification, and a fourth lens group performs a correction of focal point shift and focusing by zooming, an attachment lens of negative refractive power is detachably configured in front of a zoom lens.
Moreover, a constitution is known, in which an industrial zoom lens for a video camera is mainly formed of a focus lens part, a variable magnification lens part that varies magnification, and corrects focal shift due to the variable magnification, and a fixed master lens part that plays an image forming role. By inserting an extender lens group into a large air distance inside of the master lens part, a variable magnification focal distance area is shifted to the telephoto side.